


Guardian Current

by Anarfea



Category: Sherlock (TV)
Genre: Alternate Universe, Alternate Universe - Merfolk, Alternate Universe - Victorian, Angst with a Happy Ending, Established Sherlock Holmes/John Watson, First Time, I know things look like they can't end well for Mycroft but they do I promise, Incest, M/M, Mating Cycles/In Heat, Merlock, Mycroft Being a Good Brother, Mycroft is a Bit Not Good, Mycroft is a man-eating fish, Rough Sex, Seriously Mycroft eats humans you’ve been warned, Seriously lots of angst though, Suicide Attempt, Xeno, background Johnlock, holmescest, implied polyamory, incest is not taboo among merfolk, mercroft, merfolk sex, there is no sex involving humans in this fic
Language: English
Status: Completed
Published: 2019-06-11
Updated: 2019-07-08
Packaged: 2020-04-23 21:43:32
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 3
Words: 15,430
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19159564
Author URL: https://archiveofourown.org/users/Anarfea/pseuds/Anarfea
Summary: For centuries, Mycroft has loved and protected his clutchmate Sherlock. But over the years, they’ve drifted apart, as Sherlock has come to resent Mycroft’s meddling. Now Sherlock has a human lover, and Mycroft fears he will lose his brother forever. But he’s not one to give up without a fight.





	1. Rescue

**Author's Note:**

  * For [jinglebell](https://archiveofourown.org/users/jinglebell/gifts), [Spenglernot](https://archiveofourown.org/users/Spenglernot/gifts).
  * Inspired by [Riptide Lover](https://archiveofourown.org/works/2312978) by [jinglebell](https://archiveofourown.org/users/jinglebell/pseuds/jinglebell). 



> In 2014, jinglebell and I were hanging out in the Antidiogenes chat room and I posted some sentences from a fic I never ended up publishing, in which Janine Moriarty lies in a bathtub and compares herself to a mermaid--not the Disney kind of mermaid, but the man-eating kind of mermaid. jinglebell was intrigued, and we discussed our shared love of dark mermaids, and they were inspired to write a short ficlet about Merman!Sherlock rescuing Sailor!John from a shipwreck and absconding with him to an island where they proceed to have lots of sex during the Riptide (merman pon farr).
> 
> That ficlet, which jinglebell gifted me, took on a life of its own and grew into the novel-length fic Riptide Lover. I adored the world that jingle created, and I wanted to write in it myself. Particularly, I wanted to write about that fic’s version of Mycroft, a lionfish inspired merman, and his love for his clutchmate, betta fish inspired Sherlock. jinglebell has said that Holmescest is canon in Riptide Lover’s universe, but they did not delve into that aspect of Mycroft and Sherlock’s backstory. I wanted to. I started writing snippets, but they remained languishing in my WIPs folder as Riptide Lover went into a long hiatus.
> 
> But then two things happened. First, jinglebell finished Riptide Lover, and I re-read it and fell in love with the story all over again. Second, Spenglernot won one of my auctions for Fandom Trumps Hate. Spenglernot bid on me because she had seen my name in connection with jingle’s fic. I asked Spenglernot if she would be interested in a story set in the Riptide Lover universe. She was game. These events inspired me to pull out the snippets I’d written and piece them together with the help of my betas Tiltedsyllogism and Redscudery (who also beta’d Riptide Lover).
> 
> Riptide Lover is a wonderful novel and I recommend you read it. That said, this story was written to be accessible to those who have not. It is a stand-alone story. I hope you enjoy it.

Mycroft floated in the calm, warm water of the small coral atoll which made up his nest, his long fluked tail twitching in response to the high-pitched keening Song which traveled through the beneath. Irene and her bonded one, Mŏlle, were Singing to him, promising pleasure. They called on him every year during the Riptide -- as a courtesy, he supposed. Irene was the leader of the fiercest sorority pod, and Mycroft was the strongest male in the region. But the gesture was just a formality, as they knew by now that Mycroft would not accept. Mycroft loathed the Riptide, hated having his head clouded with base instinct. It surged within him now, urging him to Sing to the daughters of Undine, the mother of them all, to invite them into his nest, to mount them and drench their eggs in his seed, to accept their clutches back into his own brood pouch.

Other desires lurked deeper, their dark currents stirring up memories of the only Riptide which had ever brought him pleasure. Sherlock had come to Mycroft’s nest the first time he’d experienced the _lek_. Mycroft suspected he had been afraid of Irene’s fierce females, and had sought release with someone familiar and convenient. But Mycroft had responded all too willingly. His own fluke had turned colors visible only to undine and mantis shrimp, and he’d willingly surrendered his body to Sherlock’s gratification for a week entire. These were the thoughts which surfaced when he took himself in hand or pressed his knuckles into the the aching opening of his inguen.

But Sherlock had not returned in subsequent seasons, and Mycroft did not dare to court him. As a result of his resentment, the Riptide’s influence on him had lessened over the years; his skin still became sensitive and opalescent, but his red and white fingered fluke did not change color, the desperate need to fuck and be fucked lasted a mere three days rather than a week or more, and he never entirely lost his higher functions as some undine did. He was surprised the Riptide still pulled him at all, that he’d been unable to shape his body with his will like the undine who knew their sex was wrong, the ones who appeared male as fingerlings, but swam with the sorority pods until their bodies lengthened and strengthened and their fins shrank away and they became indistinguishable from the rest of their sisters.

Perhaps it was because his own will was divided. He had no desire to allow anyone, even a lover, into his territory when he had so little control over his own body, but he knew that someday, when the undine were united and the seas were safer, that he owed it to his species to breed. So far, he had found no one he deemed his equal, not even Irene, though every year she made the same token gestures of seduction. Perhaps one day, if he found her, he would carry a clutch for the great Undine herself. His body seemed unwilling to disengage from the Riptide entirely in anticipation of that eventuality, and so he continued to experience his shortened bouts of _lek_ in frustrated solitude.

Irene and Mŏlle left, still Singing, headed in the direction of Sherlock’s territory. The line of Mycroft’s spine tensed and his neck gills fluttered. Surely Sherlock wouldn’t admit them into his territory with a human on the island. There was a distinct possibility that Irene and Mŏlle would want blood if Sherlock denied them sex. They would Sing John down to the shore and tear him to pieces. No, Sherlock would run them off, would spend this Riptide alone. The thought of Sherlock shivering in his nest, rutting into his own clawed fist, aching with need, made his own cock swell inside his body. The lust of _lek_ pulled him out of his own nest and into the open sea.

He kept his distance from Irene and Mŏlle as they swam through the opening in the guardian currents surrounding Sherlock’s nest, vicious riptides of curling waves that would thwart anyone who approached, unless they passed through the channel that ran between them. They swam down the channel and approached the mouth of Sherlock’s grotto. Mycroft trailed behind, turning away from the grotto and towards the island, searching for John. Mycroft broke the surface near the section of beach where John liked to hunt crabs, but saw no one. Perhaps John had retreated to the shelter of the hideous tree he slept under. It would surely be more difficult for an undine to Sing him to the shore from that distance.

He could still feel Irene and Mŏlle’s Song resonating in the water, even though he couldn’t hear it now that his ears were above the surface. Their melody stoked his own lust, promising pain and pleasure, but Sherlock made no answer, untempted. After several minutes, they retreated, swimming away in search of some other conquest. Mycroft’s throat ached with desire. He stared longingly at the mouth of Sherlock’s grotto. But he would not be welcomed any more than Irene and Mŏlle. If John was not on the island, then he was in the grotto with Sherlock.

A human, survive the Riptide? Sherlock was mad. He might kill John in his passion, crush him, split him in half. _Perhaps that would be for the best._ He determined not to intervene. Even if he wanted to, it would be foolhardy to enter his brother’s territory when he was sequestered for the Riptide. Sherlock would see Mycroft as a threat, an intruder. Mycroft dove beneath the waves and swam for his own nest, bubbles churning in his wake. He would spend this Riptide alone, as he had so many others.

~ ~

Three days and many frustrations later, the _lek_ released him from its clutches, and Mycroft ventured forth from his nest to hunt. A school of tuna swam near the edge of his territory, and he was famished. To his irritation, he glimpsed another male undine in the water, scattering the fish. While technically he was not inside Mycroft’s territory, he was too close for comfort. Mycroft’s neck gills flared with indignation, and he swam to meet the intruder. On a closer look he recognized the undine’s abalone pink scales, the fluke stained red from _lek_. Mirko. His territory was adjacent to Mycroft’s, and he was a sometime consort of Irene and Mŏlle.

As Mycroft fanned his aural fins in a threat display, he saw the shadow of an approaching ship: small, but sleek and deadly, moving at some speed through the calm waters. Mycroft stayed back, treading water, and watched as the unmistakable mesh of a woven net was lowered over the side. Mycroft hissed. Mirko dove down, but the weighted net sank after him and then scooped, catching the undine and the tuna alike. Mirko thrashed, churning the water full of bubbles. The weight of the full net rocked the ship as her crew pulled its cargo aboard.

Mycroft swam to the surface, breaching silently, just enough to keep his aural fins above water. The ship had a black hull with a bright yellow stripe, like an angelfish. A flowing script spelled out the name _Appledore_. Mycroft had seen this vessel in his waters, and Sherlock’s, before, long ago. He had warned his brother that the ship did not cut a straight path through the water but hugged the shores of the islands near undine nests as though looking for something. _Hunting_ for something.

The humans on deck pulled the net up and over the railing. Mycroft’s gills fluttered in anticipation. Then the shrieks and wails began. A man fell overboard with a loud splash. Mycroft submerged himself, watching the crimson blood swirl through the water. The man bobbed to the surface. Dead. A second man followed, this one still alive and flailing. Mycroft’s nostrils flared. Hunger panged. But it was far too dangerous to feed here, and he needed to warn Sherlock. He dove down deep into the beneath and swam towards Sherlock’s island.

When he reached the mouth of the grotto, Mycroft treaded water outside it and made several high-pitched sounds that John would not be able to hear. There was no response. Either his brother had gone out to hunt, or he was ignoring him. Mycroft clenched his claws in frustration. But he dared not enter the grotto. It was a mortal offense to enter another undine’s nest uninvited during the Riptide. While he doubted very much that his own clutchmate would actually kill him, he had no doubt that Sherlock would attack him and that the resulting fight would be bitter. His brow furrowed. He wanted to warn his brother about the human ship which was clearly hunting undine. But maybe the threat was not as urgent as he had originally perceived. The humans had caught what they were looking for, and perhaps they would be satisfied. Still, he felt uneasy.

~ ~ 

Mycroft saw the _Appledore_ again two days later. The little ship was just offshore of Sherlock’s island. His heart caught in his throat, and he swam towards it. It was then that he heard it. A horrible, grating sound, like shells grinding together, with a high-pitched overtone that pierced his ears so he thought they would bleed. All his muscles spasmed. Instantly he swam away, but its hideous frequency still vibrated underwater. He tried to outswim it, darting away from both the ship and Sherlock’s island.

As he swam, his heart sank. He had decided not to warn Sherlock that the human vessel had captured an undine. And now he was nearly certain they’d taken another, that his brother was on that ship. He cursed himself for a coward for not swimming towards it, but the noise was so terrible as to be almost incapacitating. If he swam closer, he had no doubt it would make him lose consciousness. There was no way for him to help Sherlock, and he cursed in every language he knew.

Then, he glimpsed a choppy white wake on the horizon. Mycroft swam towards it, easily overtaking John Watson and then swimming alongside him. John did not break his stroke, but turned his head towards Mycroft.

“John Watson. I couldn’t get close to the human ship. There is a terrible sound -- I can still hear it, on the distant winds. Where is mine own brother?”

“I know. That sound is designed to impede your kind,” said John. He spat. “As for Sherlock, he’s alive but they -- they took him.”

“I knew it.” Mycroft kept his tone flat, did not let the fear and sorrow welling in him show. He didn’t understand why John was not swimming for Sherlock, or for the safety of Sherlock’s island. “Land is back that way.”

John kept stubbornly swimming. Blood seeped from a gash on his chest.

“You are going the wrong way. And you are wounded.”

John ignored him. He kept swimming. And then he began floundering. He sank beneath the waves.

Mycroft reached for him, pulled him to the surface.

John collapsed against him, falling into his arms. It was uncomfortably intimate. He treaded the water slowly, gills fluttering as he cradled John, who trembled against him.

After a few moments John began to cry. He made a low, choking sound, and tears streamed from his eyes. Mycroft had seen humans cry before, but never from this close. He wasn’t sure what he should do, if he was expected to comfort John in some way. He moved to pat John on the head, but decided against it at the last minute.

“This is all my fault,” John muttered.

No. This was Sherlock’s fault. Brave, reckless, foolhardy Sherlock. “This is not the first time that this human ship has come into mine own brother’s territory. I warned him many moons ago it had returned. Mine own brother knew the risks.”

John said nothing, taking everything in. He continued to weep silently. The waves lapped the tears from his cheeks. At last he said, “Right. That’s enough of that.” John rubbed his hand over his face, wiping his tears, then disentangled himself from Mycroft. He began to try to swim, still headed the wrong way.

“What are you doing?”

“He took Sherlock from me. He can’t have him.”

Mycroft swam in front of John, cutting him off. “So you are going after the ship alone? John, you are not even going in the right direction.”

John brought his hand down against the water with a resounding slap. “I may not be bloody undine, but if there is one thing on God’s green earth that I can do, it’s navigate. At. SEA. I’m going to the islet where Sherlock keeps his skeleton and buried treasure. Why don’t you put your damned wave weaving to use and help me get there, eh?”

Mycroft blinked, eyebrows rising.

“Well? Either you can make yourself useful and help me, or get out of my way.”

No one spoke to him this way save Sherlock. That a puny human would --

“USELESS!” John yelled, swimming against the waves which pushed back against his battered body.

Mycroft reached for John’s arm, then wove the waves before them, smoothing them out to make a path. He could not save Sherlock alone. Perhaps he could help John carry out whatever plan on which he was intent. Swimming to an islet. With…. “Sherlock has buried treasure?”

John laughed “He does. It’s unbelievable.”

The existence of the treasure was not what surprised Mycroft. His brother had a penchant for human artefacts, and loved shipwrecks, had been exploring them since he was a fingerling. Still, he couldn’t believe he’d never seen his brother stashing things away.

“But that’s not why I’m going there.”

“Why are you going there?”

“There’s a dinghy. I need it if I’m to catch up to them --”

Mycroft paused. John meant to take on the whole ship full of other humans. Mycroft would be unable to help him because of the machine --

“No, no, don’t stop swimming. Damnit Mycroft!”

“John,” Mycroft reasoned. “Humans are dangerous. See how they have wounded you already. They will kill you, and mine own brother both.”

“Humans are dangerous, Mycroft,” John agreed, squeezing Mycroft’s forearm. “I am not letting them take Sherlock. You’re going to help me get back to the Appledore - or at least, as close as you can come. I’ll take care of the rest. After all… I’m human, too.”

For the first time since he’d heard the dreadful noise, Mycroft hoped.

~ ~ 

The dinghy John had swum in search of was a pathetic thing, powered by two oars, with a crack in its small hull. It was half-filled with sand.

John used the oar as a trowel and dug the boat out.

Mycroft dipped below the water, listening for the hateful sound. It carried through the ocean like a low shrieking wail. He wrinkled his nose, then surfaced to watch John push the little boat down the beach into the water.

Mycroft blinked. “Hm. It actually floats,”

“Of course it floats.” John was indignant. “Now, see here. I’ve never heard of a rowboat catching up to a clipper. In fact… I’d say it’s impossible.”

Mycroft drew himself up out of the water. What did John take him for? He pressed the side of the small vessel to see if it would tip. “For a human alone it may be impossible. If this boat does not break, catching up to the humans won’t be a problem.”

“Won’t it? Do you intend to move this, then?” John smiled impudently.

“Yes.”

“If luck smiles upon us, we’ll find that clipper.”

Mycroft scoffed. “Only a fool relies on luck, John Watson."

“Then I’m a fool,” said John. He wiped the blood on his chest and fussed with the oars. “And foolishly, I will rescue Sherlock, if it’s the last thing I do.”

“I know where the human ship is.”

John started.

“Sound travels well in the beneath. While you were digging out this improbable little ship, I listened for the hateful noise.”

“You can hear Magnussen’s machine from this distance?”

He imagined he would still be able to hear it from a far greater distance. It was a noise that should not be in the world, and it tore through the water like a rip in the fabric of creation.

“Locating mine own brother will not be a problem, provided this vessel doesn’t sink. But if I venture too close I expect I shall become incapacitated.” It would become increasingly difficult to focus on weaving wave the closer he got as well, but he didn’t want to frighten John with that.

“No, no, there’ll be none of that. Leave the machine to me. I will find a way to silence it."

“I hope you will,” Mycroft picked at a piece of kelp floating in the water. He couldn’t meet John’s eyes. Life in the ocean was dangerous. And Sherlock was reckless. Mycroft had long known his own clutchmate might meet his end in the jaws of a Named One, or in a territory war with another undine. But for him to be subjected to the cruel whims of humans, to die alone in torment while Mycroft was helpless to save him -- this he could not bear. Sherlock’s loss would break his heart.

“We’ll get him back. Right. Well. Let me just -- I’ll, that is, I’ll see if there’s anything useful left before we set off.”

Mycroft waited at the beach while John went inland to wherever Sherlock kept his treasure. Mycroft was curious about his brother’s hoard -- but not enough that he would be willing to wriggle along the beach like an eel to see it.

John returned carrying a bottle.

“What is that?” Mycroft held the little boat steady as John climbed inside. For a moment he thought the vessel would sink low enough to start taking on water via the crack, but it bobbed to the surface.

“Booze.” John yanked the cork out with his teeth and spat it out. It landed with a plop in the water and bobbed away. Then he took up the oars of the little boat and began to row. “Let’s see what this old girl is capable of.”

Did John truly think he could row his way to the _Appledore_? “Allow me,” said Mycroft, and he took a deep breath and began to weave. The water before them flattened and smoothed, and the water behind them furled into waves and pushed the dinghy out to sea. Mycroft swam behind it, and the boat moved as though it had sails.

John sat and drank. Mycroft supposed it eased the pain of his wound. One of his nipples had been shorn off, and the place where it had been seeped blood. It seemed John, too, had lost an ornamental body part in Sherlock’s service. Mycroft’s missing fin did not pain him anymore, but its absence was a constant reminder of the lengths he’d go to to defend his brother.

Mycroft wove wave and swam. He pushed the little boat forward with the power of his will, flattening the waves before them and pushing the waves against the boat from behind. Cutting a clean, v-shaped wake through the water. He guided them towards the sound, which got louder the closer he swam. It vibrated his aural fins, his jaw, his whole body. Every undulation of his tail brought him closer to the hateful noise. But he had to reach Sherlock.

_What if I am too late? What if the humans kill Sherlock? What if they bring him back to one of their settlements as a prize? What if they return to hunt more undine?_

The noise made it difficult to focus. Weaving the waves was taxing him to the utmost. He was growing tired. And hungry. So hungry.

He scented blood. The human in the pathetic ship was bleeding. Mycroft’s throat was parched. He floated up, gills flaring.

“Mycroft?”

The human leaned over the side of the little boat. A drop of blood fell in the water, blooming like an anemone. Mycroft could taste it. He breached the surface, throwing himself on the little boat and clawing his way towards the human. Humans had taken Sherlock. This one would pay.

The vessel swayed and tilted beneath him, half-sinking beneath the weight of his tail.

The human gasped and flailed, mewling nonsense.

Mycroft lapped at the wound on the human’s leg, coating his tongue with hot copper. He hissed in anticipation.

“...Sherlock. Don’t you want to save Sherlock? Your brother?”

His own brother’s name cut through his bloodlust.

“Sherlock needs us. But you can’t get close to the ship without my help. Kill me now, and you will never see your brother again. Mycroft, please.”

The blood was still bright on his tongue. But the words entered his ears.

 _Sherlock. I must get to Sherlock. This human -- my own clutchmate’s human -- will help me find Sherlock_.

Slowly, Mycroft wriggled backwards into the water. The boat tilted dangerously from side to side, but the human -- John -- kept his seat in it.

Mycroft treaded the water slowly, taking deep breaths through both lungs and gills. “John?” he asked tentatively.

No answer.

“John?” He asked again.

“Yes?”

“My apologies.”

John remained silent.

“I don’t know what came over me. I usually have, ah, better control. The wave weaving is strenuous, and I -- well. Never mind that.”

John was hiding in the flat bottom of the little ship. Mycroft couldn’t see him from this angle, but he knew he was listening.

“John? Please come out.”

At last, John sat up, peering at Mycroft through his fingers like a child pondering a … monster. That is what Mycroft must seem to him.

“As you said. My brother needs us. Shall we?”

John nodded.

Mycroft wove the wave again, and swam on.

~ ~

The sun was a bright ball of heat, high in the sky. Mycroft hated it. It was not his habit, nor that of any undine, to be active at noon. Males preferred the twilight hours, when the sky was rosy, not stark white. The heat made it hard to concentrate, though it was nothing to the noise. The noise sapped his strength, weighed heavy on his fins. John lay in the boat and drank.

Mycroft swam towards the sun until it tilted low on the horizon. Then he swam into the flaming orange sunset, pushing the little boat before him. Every passing minute brought him closer to the noise. It was vibrating his skull, now, making his teeth chatter. Moonrise brought him no reprieve -- the heat fled, but the noise grew ever louder. His eyes began to roll in his head and he verged on blacking out. Still, he didn’t want to stop. The evil black and yellow boat was just up ahead on the horizon. And Sherlock was on board.

John took up the oars and began to row, pulling away from Mycroft, who was grateful for the relief, though he would never have asked. Mycroft swam away from the hateful noise, but stayed close enough that he could watch John row the little boat alongside the bigger ship and then slip, splashless, into the water.

Mycroft’s gills heaved and flexed, and his fins flared in the water, venomous spines at the ready. He could do nothing to assist John, not as long as the horrible machine blared on. But he would be ready as soon as John silenced it.

John climbed the netting hanging on the side of the boat and pulled himself on deck. Mycroft treadled his tail, took his lower lip between his teeth and bit it until the blood flowed. The pain cut through the noise.

_Soon._

 ~ ~

The pathetic boat drifted after John abandoned it. It was close, too close to the _Appledore_. Any human who looked out over the railing would see it. He reached out with his will for the dinghy. But he was tired, so tired. And the noise rattled his jaw so hard his teeth ground together. Still, he pulled the water surrounding the little boat just enough. It drifted towards him, away from the ship and John Watson.

John had disappeared from view, beyond Mycroft’s help now. Mycroft could do nothing but watch and wait for John to silence the machine. He took deep breaths, flaring his gills in the water, trying to make the most of these precious moments of rest. As soon as the noise stopped, it would be time to fight.

The moon cast a silver glow over the water. The waves lapped at his chest. Mycroft treaded water and waited. And waited. A faint splash pricked Mycroft’s ears. He strained his eyes in the twilight gloom. Nothing. He dove beneath the surface. There. The clumsy strokes of a human swimming through water. Had John thrown this one overboard?

Mycroft watched the man swim towards the dinghy, still drifting on the water. He hauled himself upwards out of the water and into the tiny boat, nearly capsizing it. Then he began to row. _To me_ , Mycroft willed.

Another splash. A second human jumped overboard and swam for the rowboat. John must have had some success then, if they were abandoning ship. They feared him. Mycroft’s heart swelled with pride. He pulled the little boat closer.

And then, suddenly, the noise spluttered out. Mycroft sighed in relief, aural fins still throbbing with the memory of it. He took deep breaths, savoring the silence. It was broken by a gunshot. Mycroft hissed, hoping for John’s sake the shot hadn’t hit home. Then he swam for the rowboat.

For the second time today, he leapt from the water over its small hull. The humans screamed and flailed as the boat rocked under them. Mycroft reached out with his claws, raking them down the side of the closest human. The man shrieked until Mycroft tore his throat out with his teeth. The blood was hot and rich and spurted into his mouth. The second human moaned, bringing his hands to cover his eyes as though that would make him invisible. Mycroft ignored him, instead ripping the flesh from the body in his claws. If he were to be of any use to John in this fight, he needed to feed.

The _Appledore_ began to drift. It listed towards the dinghy, perilously close. Mycroft overturned the small boat and dove beneath the waves. He swam clear of the ship as the _Appledore’s_ keel scraped the coral reef surrounding a nearby island with a harsh, grating sound. The vessel ran aground, flipping onto its side and spilling its remaining, screaming passengers into the surf. Sherlock -- in a tangle of net and caudal fins -- fell into the sea.

Mycroft dove for him, pulling his brother into his arms. “My own clutchmate,” Mycroft crooned to him. “You’re safe.” Mycroft tore at the ropes with his claws. Sherlock flailed, churning the water white. The two of them peeled Sherlock’s fins free of the lines.

“Feed,” Mycroft urged. “Regain your strength.”

Sherlock’s eyes narrowed, pupils tightening into a W shaped squiggle. He opened his mouth and made a single click.

His promise. Mycroft had forgotten. That wretched, stupid promise John Watson had wrung from him:

_I promise not to intentionally kill any more humans._

Sherlock had so sworn, and evidently he had broken his oath in his escape. He had broken a promise, and Undine had stripped his voice from him.

 _Mine own brother_ …. Mycroft reached for him. _What have you done?_

But Sherlock ignored him, tearing free of the net and swimming for the open ocean. Mycroft trailed after him, uncertain whether to follow or to see if John needed his assistance at the beach. _John can handle himself,_ he decided. He dove deep and swam for Sherlock.

But his brother evaded him. Sherlock was faster than Mycroft, sleeker, and his tail was inky black and blended in with the dark water. He was not at his swiftest, having spent hours caught in a net, suffering from the sound of the machine. But then neither was Mycroft, who had exhausted himself with his wave-weaving. In the end, he let his brother go. Sherlock had suffered a great loss, and would need to retreat and to mourn. Mycroft decided to return to the little island where the _Appledore_ had run aground in search of his brother’s… lover. There was no use in denying what they were now. John was Sherlock’s lover, and Mycroft would ensure he was safe. Once Sherlock had come to terms with his loss, he would seek to recover John. Mycroft would find him first.

~ ~

Mycroft swam back to the island where the _Appledore_ had run aground and edged as close as he dared to the beach, eyeing the silver-haired sailor near the water. He made a low hum and a series of clicks in his throat. The man tilted his head, straining for the sound, and Mycroft sang the barest suggestion of a Song, weaving together the memories of cool spring mornings and the laughter of human children combing the beaches for driftwood and shells. The sailor made his way down to the water, wading out until he stood waist deep and Mycroft could sidle up beside him.

“Good evening,” Mycroft said in his sweetest, most soothing voice. “My name is Mycroft.”

“I’m Lestrade,” said the sailor, wary. He glanced from Mycroft’s teeth to his claws and licked his lips. “Are you going to eat me?”

“I mean you no harm,” said Mycroft. “Where is John Watson?”

“Are you going to eat him?” Lestrade demanded.

Mycroft smirked. “No. He saved my brother’s life.”

“Then you can save his!”

Mycroft’s brows knit.

“He needs a doctor, mate. He’s shot through the leg and in a bad way.”

Mycroft’s heart pounded. John had been wounded. The shot he’d heard earlier had found its mark after all. If he died -- “I will take him to the human settlement.”

“How?” The sailor gestured to the remains of the _Appledore_. The keel was split in two. The figurehead of a weeping angel lay on its side on the beach, next to broken bits of flotsam and the vestiges of the horrible machine.

Mycroft closed his eyes and reached out through the water for John’s pathetic little boat, directing the tide to pull it towards him.

Lestrade blanched as it bumped against the shore.

“Right. I’ll go fetch him, then.”

“Please hurry.”

Lestrade jogged back up the beach, and Mycroft sank low in the water, treading it with his tail. There was no sign of Sherlock.

Lestrade returned after what seemed an eternity, John’s limp, unconscious body in his arms, blood soaking through both their trousers. Mycroft dipped entirely beneath the surface when another, taller, darker-skinned man ran up the path behind them. For a few moments it looked as though they were having an argument, but soon they seemed to come to an accord and the second man lifted John’s legs and helped Lestrade to carry him into the boat. The absurd vessel sank low with their combined weight, and Mycroft worried the split high on its side would fall below the waterline and make it take on water.

He lifted his head above the waves and the dark-skinned man gave out a yelp and flailed for the oar, waving it at him. The toy boat nearly capsized. Only Mycroft’s hands on its prow steadied it. He pulled them back before the oar smashed down on his fingers.

“Don’t!” Lestrade shouted. “He’s with us!”

The man’s eyes narrowed. He didn’t strike at Mycroft again, but he didn’t set the oar aside, either.

“Sorry I didn’t mention it, Omadi, but I didn’t expect you would come. This is the other siren’s brother. He’s going to help us because we saved his brother’s life.” He stared pointedly at Mycroft. “Aren’t you?”

“I shall endeavor to be of assistance.” Mycroft did his best to to sound human, or at least civilized.

Omadi begrudgingly sat down and returned his oar to the water.

“That won’t be necessary.” Mycroft raised his hands to the stern and guided it out to sea, parting the waves before it and pushing through the path he wove with his tail. “I can push much faster than you can row.”

A slight rippling beneath the water was all the warning he had before Sherlock rammed into him beneath the waves, raking his claws down Mycroft’s sides and shearing off scales. He released the boat and dove beneath the surface, coming face to face with his brother, locking eyes. Sherlock’s neck gills were flared and his claws were curled, trailing blood in the water. His tail thrashed behind him.

Mycroft flared his own plumage, extending his red and white dorsal spines. “Don’t interfere.” _Please_.

Sherlock let out a series of infuriated clicks.

“He has a grievous wound, Sherlock. If you do not permit me to take him to the human doctors, he will die.”

His brother shook his head and launched himself to the surface, pushing himself up into the rowboat. Water sloshed over the sides.

Mycroft grabbed him by the waist and pulled him back. The boat nearly rolled again.

“Don’t!” He pulled Sherlock around, forcing him to look at him. “Mine own brother, you will regret this! _”_ _You will never forgive me._

Sherlock thrashed in his arms, kicking at Mycroft with his tail and breaking his hold. He doubled back just as quickly, claws outstretched. Mycroft grabbed his wrists when Sherlock dug into his chest and deflected his momentum, rolling in the water with him.

Above them, Lestrade and Omadi rowed frantically, and the little boat pulled away.

Mycroft dove deep, pulling Sherlock with him, and did something he’d never done--turned and raked his dorsal fin across his brother’s body. The spines split his brother’s flank, releasing their venom into his skin. Sherlock thrashed, his blood clouding the water. Mycroft grasped him tight, arms wrapped around Sherlock’s chest, and held him in place until his writhing subsided and his eyes drifted closed.

_I’m sorry, brother mine. It had to be done._


	2. Clutchmate

_Before_

Mycroft patrolled the border of his territory and Sherlock’s, which was a large ring, as his own territory completely surrounded his brother’s. He had gradually driven out the other undine that inhabited the waters adjacent to Sherlock’s -- for his brother’s own protection. Sherlock did not get along with others of their kind at the best of times, and had nearly been killed in a territory dispute when he was a fingerling. Mycroft was better at negotiating with other undine -- and at fighting them, if it came to that. He was bigger than Sherlock, and the venomous spines on his dorsal fin gave him a combat advantage over most undine. Sherlock resented the encirclement, but there was very little he could do about it.

Mycroft surfaced above the waves, looking in the direction of Sherlock’s island.

“Sherloooooock!” John’s cry was distant, but audible. Mycroft’s aural fins twitched at the sound and he dove under the waves and swam in its direction. If John was in danger, Sherlock would come to his aid. And Mycroft would come to Sherlock’s. 

He swam swiftly, propelling himself with his powerful tail. As he grew closer, he scented blood. He bared his teeth and extended his claws forward.

Sherlock had engaged Olizarat. The giant shark snapped at him as Sherlock darted away again and again, whirling in a cloud of black tail and white fins. Blood trailed from one fin, slashed in two by the shark’s sharp teeth. Sherlock had left his marks on Olizarat as well; his claws had torn gouges in her barnacle-covered hide, and swirls of blood rose in the water.

Mycroft flared his dorsal fin, extending his venomous spines, and dove beneath Olizarat, raking his spines across the Named One’s belly. The creature was far too large for the venom to intoxicate it, but it would certainly cause discomfort.

Olizarat whirled toward him, maw gaping wide, revealing row after row of coral-sharp teeth. Sherlock threw himself at her snub nose, clawing the sensitive nostrils. He wrapped his lower body around hers and tore at her face. Mycroft went for the vulnerable gills, rending the pink flesh with his claws, digging deep until he had pushed his arms in past the elbows.

As Olizarat writhed, she twisted Mycroft’s right arm, wrenching his shoulder from his socket. Pain lanced through his shoulder and neck and she shook him back and forth as though he were a seal.

Again, Olizarat snapped at Sherlock, lashing her head side to side and trying to fling him off. Her jaws found nothing but saltwater as Sherlock danced out of her reach, still tearing at her face. He dug his claws into her upper and lower jaws, pushing them open even as she tried to slam them shut.

Then he Sang, a short, sharp, low-pitched sound intended to incapacitate. Olizarat slumped, jaw slackening in Sherlock’s arms. Sherlock shot Mycroft a look. _Stay clear_.

Mycroft pulled his arms free of the mess of chum Olizarat’s gill flesh had become and swam free. His shoulder ached, and he let his right arm hang at his side, pulling himself along with his left arm and pushing himself with his tail.

Sherlock whirled his tail and flexed his shoulders, pushing Olizarat’s upper and lower jaws apart until the flesh at the corners of her mouth tore. Mycroft would have liked to help -- Sherlock’s muscles were corded with effort -- but his own shoulder throbbed with pain. Sherlock parted the jaws like a mussel shell, overextending them until they ripped, first the ligaments and tendons, then the bone, which crunched and snapped as Sherlock rent the ancient flesh.

Thus ended the life of Olizarat the Destroyer. Mycroft was not sorry to see her die -- Olizarat was perhaps not as malevolent as the Peacekeeper, fiercest of the Named Ones, but she had been vicious and cruel and had killed many an undine. The seas were safer without her.

Sherlock let her body, head torn in two, drift downward, where it would become food for the crabs and fish. Apt, albeit undignified. Mycroft was grateful that undine turned to foam when they died. His corpse would not become a feast for the deep when the abyss claimed him.

Still favoring his arm, he paddled back over to Sherlock, who was treading water, gills heaving, blood coiling off his claws in red plumes. Mycroft reached for him, and Sherlock grasped his forearms and drew close till their foreheads were nearly touching. John must not hear what they had to say to one another.

Mycroft made small noises deep in his throat that would be inaudible to human ears. “You could have died. And for what? Your plaything?”

Sherlock furrowed his brows. “I had everything well in hand. I hardly needed you sticking your squid-beak into the situation. All you did was cause yourself injury.” He dropped Mycroft’s forearms and swished him away with a gory claw.

Mycroft rolled his eyes. He doubted very much that Sherlock could have defeated Olizarat alone, and he suspected his brother knew it. Still, given their history, he had not expected gratitude.

“Other sharks will come to feast on Olizarat’s corpse,” said Sherlock. “I promised I would not forcibly keep John in mine own nest,” Sherlock gestured to John, submerged nearby and watching them, “but it is not safe for him to stay here.”

What did Sherlock mean by this? Was he asking Mycroft’s opinion on whether this would constitute breaking his promise, if Undine would take his voice from him? Mycroft doubted it. Sherlock had sworn not to _keep_ John in his nest, not that he wouldn’t _bring_ him to it, by force, if necessary. And Undine was pedantic. He nodded slowly.

They both turned to look at John, who scrambled away, swimming backwards like a crab scuttling on a beach. Sherlock swam for him. Mycroft caught John’s eyes and tilted his head. _I hope you appreciate what he did for you._

John nodded in what Mycroft hoped was recognition.

Mycroft drew his throbbing arm close to his side and swam away, driving himself with his great fingered tail. He glanced back over his shoulder to see Sherlock reach out for John.

John swam hard for the surface, snatching a breath of air.

Sherlock pulled him under, gathering him into his arms. John kicked and flailed, thrashed and squirmed, even sinking his teeth into Sherlock’s aural fin.

At the memory of Sherlock’s teeth, a phantom pain twinged at the place where Mycroft’s missing fin had been torn from his body. He had been trying to protect his own clutchmate from sharks. Mycroft smiled at the bittersweet irony. Then he swam for his own nest.

~ ~

_Now_

Mycroft drew Sherlock’s unconscious body into his arms. They were too far from his own nest for him to bring Sherlock home, but he pulled him towards a semicircular formation of coral that provided some scant shelter. Even buoyed by the water, Sherlock was heavy, and towing his body was awkward. Mycroft cradled Sherlock, watching the water toy with the tendrils of his black hair, swirling around his white face and the tiny iridescent scales dotting his cheekbones and eyelids.

_Whatever happened to us?_

Sherlock had admired him once, looked up to him. No longer. That was Mycroft’s fault -- his miscalculation that first Riptide…. But things had gotten better in the centuries since then, and they’d achieved detente, if not amicability.

Until John. Mycroft had never imagined something as paltry as a human could come between them, but he had. Now Sherlock resented Mycroft’s every attempt to assist him, and their bitter arguments had degenerated into outright fights. Mycroft had even resorted to using his spines against his own clutchmate.

But John was gone for good, now.

Sherlock’s eyelids snapped open. He flailed in Mycroft’s arms, tongue clicking in the back of his throat. His voice would never sound again. But he didn’t need to use words for Mycroft to understand his meaning.

_Where is John?_

“Two of the sailors took him to the human settlement to the northwest of your island.”

Sherlock wriggled in Mycroft’s grasp, but Mycroft held him. Sherlock bit Mycroft’s arm, drawing blood.

“Do not pursue him, mine own brother. He will not be glad to see you.”

Sherlock clicked in protest.

“I know you shared a Riptide. But you are letting your mind be clouded by _lek_. He does not love you. Humans cannot love undine. They are fascinated, yes, but in the end they always see us as monsters.”

Sherlock hissed.

“After you and I -- I myself had a human lover. I did not dare risk taking him to my nest, but I met with him in a tidepool near the shore where he liked to fish.”

Sherlock twisted in his arms, scrutinizing him.

“He was called Daniel. He was beautiful, sun-browned with dark, curly hair, and I cared for him. I swam to meet him every day, and we spoke together for hours and hours. He answered my questions about humans, and I in turn his about undine. But then one day, he did not come. I waited for him, all that day, and the day after, and the day after. But he didn’t come to me. I reduced the frequency of my visits, but I remained hopeful. Then one day I saw him walking the beach with a human female. She had a heavy belly. I knew then that all the time we had spent in company, he hadn’t truly been mine own. His heart belonged to another, and he chose her. She was his bonded.”

Sherlock had relaxed in his arms, listening to his story. But as soon as it was done, he began to squirm again. Mycroft held him tighter, digging his claws into Sherlock’s arms.

“I do not tell you this to hurt you, brother mine. Only to help you to see the truth. John may have developed a certain fondness for you because you were his only companion on the island. But it is a sick fondness, born of loneliness and need. Now that he is among other humans, he will forget you. Even if you swim to the human settlement, what will you do? You have no voice. You cannot call to him, and he will not look for you.”

Sherlock clicked again, but some of the sharpness had gone out of it.

“I know what you are thinking. When I offered to take John to the human settlement, he refused. But that is not because he wanted to stay with you. It was because he did not trust me. As soon as he had the opportunity to leave he swam towards the Appledore. And look how that ended for you! You might have died, trying to pursue him.”

Sherlock scoffed, but Mycroft knew it was bluster. His brother had to know how close he had come to death at Magnussen’s hands. Still, Sherlock was reckless with his own life and fear of death was unlikely to sway him. He had to believe John didn’t truly care for him.

“John enlisted my help to save your life. But this was again not because he cares for you, but because you saved his life when his ship was wrecked. That debt is paid, now. He has no further obligation towards you. He will not return.”

Sherlock slumped in Mycroft’s arms, defeated. Mycroft ached to have hurt him, and yet he was glad to have gotten through. He stroked Sherlock’s hair. “I am sorry, mine own brother. I know this wounds you. But you are not the first to feel such pain. All hearts are broken. Caring is not an advantage.” Confident he wouldn’t swim away now, Mycroft let Sherlock go.

Sherlock swam towards his island.

Mycroft bit his lip, watching him go. His brother would grieve John’s loss terribly, he knew. But it was for the best. Twice now, Sherlock had almost died because of John Watson. John was Sherlock’s greatest weakness, just as Sherlock himself was Mycroft’s. There was nothing to be done for Mycroft’s frustrated love, for his own broken heart. But Sherlock’s would heal in time. It must. If he died of his grief, Mycroft would follow soon after. The loss of his clutchmate would break him, and they’d both turn to foam on the sea.

~ ~

Mycroft left Sherlock alone for the time it took the moon to wane and wax again. He worried about Sherlock constantly, but did not approach his nest, swimming well outside the guardian currents which encircled his brother’s island. Sherlock had suffered two great losses. His voice -- his ability to speak and to Sing and command other creatures -- and his lover. He needed time and space to mourn. But when the moon was full and still Sherlock had not left his nest, Mycroft went in search of him.

He swam between the guardian currents into the mouth of Sherlock's grotto. It was empty. The great rock where Sherlock liked to lie and sun himself in the light that shone through a hole in the ceiling of the cave was bare. No one save a small fish swam in the water which filled the bottom of the grotto. It was silent save for the sound of water dripping on the walls. Mycroft's heart beat fast. Where was his brother? Had he swum past Mycroft's patrols, into the deep ocean? Or was he on the island? Mycroft resolved to check the island first. He swam out of the grotto and circled back to the shore.

Sherlock lay sprawled on the beach, caudal fins strewn like a haphazard mat of kelp, curling at the edges and drying out in the sun. His gills flared open and closed, bleeding at the edges where he’d abraded them against the sand. The beach was marred with scores of serpentine tracks where he’d crawled up the beach, retreated to the water, and then crawled onto the beach again, evidently trying and failing to beach himself.

“Sherlock!” Mycroft surged forward on the crest of a breaking wave, letting it carry him inward and then rocketing himself as far as he dared onto the sand.

Sherlock tilted his head towards him and opened one eye. The nictitating membranes at the corner of his eyelids were red.

“Sherlock, you must come back!”

A halfhearted attempt at an obscene hand gesture was his only reply.

Mycroft pulled himself up on his elbows and began to wriggle forwards, closing his gills tight as he snaked across the sand, dragging the dead weight of his fins behind him.

Sherlock clicked furiously, aural fins flared in a threat display, and scuttled further away from him, rolling onto his belly and clawing his way forward in the sand.

It seemed pointless to chase him inland until both of them beached themselves, so he retreated to the surf, coiling himself upright atop his tail. He began to hum, low at first, in both pitch and volume, more of a vibration than a sound.

Sherlock shook his head furiously.

Mycroft ignored him and began to Sing.

He started with a single note at the lower edge of his range, a single long, sustained sob containing all the loneliness he had ever felt. As his voice swelled, he modulated the melody, imparting the humiliation and sorrow of Daniel leaving him for a human female, the frustration of refusing the Song of the mermaids outside his nest each brief, bitter Riptide, the betrayal of Sherlock’s teeth tearing at his own adipose fin, and the worst grief, the loss of Sherlock himself. He layered an overtone atop his Song, whistling around the melody. Every pain he’d ever felt, washed away in the soothing salt water, the hard edges his anguish worn smooth as a pebble rolled across sand for centuries.

Sherlock tilted his head to the side, aural fins twitching as he listened. He shivered.

Mycroft wove in a counterpoint of joy, recalling all the dusks and dawns they’d spent together, the shared heat of their single Riptide, the shared victory of Olizarat’s blood in the water.

Sherlock’s lips parted and his throat gills were quivering.

_Come back, brother, come back. Human hearts are fickle and even when they are steadfast, human lives are short. Do not throw away your own long life for him, offering it up on this beach as though you were one of these crabs._

They marched inexorably towards the ocean, a shifting phalanx of chitin and claws. The seabirds circling the sky dove into the water and drowned. Mycroft regretted defaunating Sherlock’s territory, but his brother was strong, and everything weaker than he would break before Mycroft could bend his will.

Sherlock crawled forward, claws scraping deep troughs in the sand, tail eeling behind him. His brows were furrowed and his breath came in ragged huffs.

_Come back to the sea, brother. You have lost your voice but you have still your own strong tail; you are the ocean’s and the ocean is yours, come home._

Sherlock’s pupils thinned to squiggles, and he upraised his palm and bisected it with his claw, digging deep on top of an old scar. Blood oozed from the wound, thick and clotting, signaling increasing dehydration. Sherlock snarled at him and crawled back up the beach, the Song’s spell broken.

It didn’t matter. Mycroft was close enough to the shore that he could weave the waves into a tidal surge up the beach and ride atop their crest. He snatched Sherlock into his arms. Sherlock hissed and bit him, but he was weak with exposure to sun and sand, and Mycroft gave a mighty shove of his tail and pushed them both out to sea.

As they rolled in the water together, chest to chest, Sherlock grasped tendrils of Mycroft’s hair with his claws, pulled him close, and pressed their mouths together. For a split second, Mycroft expected his brother to bite his lips. He tensed against Sherlock, prepared to push him away. But Sherlock merely opened his mouth against Mycroft’s, licking at the seam between Mycroft's closed lips with frustration. Mycroft softened his mouth and let Sherlock press his tongue inside, strain for Mycroft’s past the rows of pointed teeth.

_Kissing._

They had never done this before, but Mycroft remembered the word, and, as Sherlock licked into his mouth, the motions. He had done this many years ago, with Daniel. He moved his tongue against his brother’s, swallowing seawater. Sherlock wrapped the length of his muscular tail once around Mycroft’s body, pressing tight against him. The sharp curve of Sherlock’s cock emerged from the v-shaped slit of his inguen, and Mycroft let his pelvic fins fall open, edges fluttering out at his sides, and raised his hips in silent offering.

Sherlock grasped him tight with the claws at the tips of his pelvic fins, digging deep enough to draw blood, and rutted against Mycroft. The weight and heat of Sherlock’s tumescence brushed across his vent, but Sherlock didn’t breach him. Mycroft hissed, blowing bubbles into Sherlock’s mouth, and raked his claws down his brother’s back. Sherlock bit Mycroft’s tongue as he finally pressed inside. Salt and copper filled his mouth, and rusty plumes swirled around them.

Sherlock continued kissing Mycroft as he drove inside him, cradling Mycroft’s head in his hands. It was strange, to kiss, to not look into Sherlock’s eyes as he received him.

_Who are you imagining with your eyes closed, brother mine?_

He let his hands drift down the nubs of Sherlock’s spine, hovering over his sides before letting his palms skate over his brother’s gills, which flared at his touch. He folded his pelvic fins around Sherlock’s hips, brushing his small grasping claw against Sherlock’s sensitive dorsal fin. Sherlock undulated fiercely into him, but Mycroft knew it was grief driving his hips, not lust. He moved his own powerful tail in synchrony with his brother’s, meeting him thrust for thrust, smashing their bodies together with a force that would split a human in half. 

_You cannot pretend I am other than I am, anymore, Sherlock. Look at me._

Sherlock obliged, breaking the kiss and licking blood from his pointed teeth. His pupils had tightened into horizontal zigzags. Mycroft met his feral gaze, raising his hands to Sherlock’s face and running the sides of his fingers along the sensitive edges of his aural fins, brushing the pink slashes of his open neck gills. Sherlock made an appreciative click at the back of his throat. The truncated sound tore something inside Mycroft. His brother should hum, moan, cry out, but he’d foolishly bound himself in a twisted, unfair promise. John had silenced him.

Something of his grief must have shown in his face, because Sherlock abruptly snapped his head to the side and bit the sensitive webbing between Mycroft’s fingers. Mycroft gnashed his own teeth to signal his displeasure, but slipped his claw into his brother’s mouth and let him suckle the blood there. Sherlock’s eyelids fluttered closed, and Mycroft knew he’d lost him to memories of John, again. Mycroft bore the knowledge with silent resignation.

The ragged roll of Sherlock’s hips signaled he was close to his peak, and Mycroft intended to arrive with him. He clenched and unclenched his vent, fiercely, rhythmically tugging at Sherlock’s cock. The reciprocal surges of their caudal fins churned the water around them white. Sherlock cried out wordlessly as he broke shuddering against Mycroft, digging into his hips with both sets of claws and burying himself until his penile barbs pressed past the edges of Mycroft’s vent.

Mycroft let out a groan deep in his throat and curled his body up into Sherlock’s, arching his neck back. Sherlock sank his teeth deep into the meat of Mycroft’s shoulder. He spasmed and grabbed the bases of Sherlock’s pelvic fins, digging his own claws into the nerve-rich tissue. Sherlock pulsed inside him again and again, filling Mycroft’s brood pouch with hot seed. His own climax overtook him as he squeezed Sherlock with his internal muscles one last time.

For a few moments they floated idly. Then Sherlock released his shoulder, laying a kiss atop the wound, which seeped copper into the water. Mycroft wrapped his tail once around his brother, draping his heavy caudal fins on top of Sherlock’s, keeping them entwined. He let go of Sherlock’s hips and stroked his back, trailing the tips of his claws over his shoulder blades. Sherlock began to tremble against him, lightly at first and then with increasing violence. Mycroft gripped Sherlock tight and undulated his tail, rocking him.

_Hush, brother mine. Be calm. Be still._

~ ~

_Long Ago_

Mycroft lay entwined with Sherlock, tails wrapped around each other, flukes fanned together, Sherlock’s back against his chest. He nibbled the edges of his brother’s aural fin--seafoam green with _lek_. Sherlock hummed and stirred against him.

“Again,” he said.

“Yes,” Mycroft agreed.

Then he rolled over, disentangling his body from Sherlock’s, and pressed the lengths of them together, chest to chest, inguen to inguen. He released his cock, letting it protrude from his body. Sherlock arched against the serpentine curve of it, whining with need. Mycroft pulled back, floating above him, and watched himself press the oxblood-colored head of his cock in between the smooth black scales of Sherlock’s vent. He grasped Sherlock’s hips with the grasping claw at the tip of his pelvic fins and glided in slowly, stopping just before he slid home.

Sherlock moaned, deep in his throat, neck gills flaring. He jerked his hips up, pushing Mycroft the rest of the way inside. Mycroft cried out as Sherlock’s tight vent clenched down on his penile barbs. Pleasure zinged up each protrusion. He snapped his hips, pulling out of Sherlock, then pushed himself home again.

“Yes,” Sherlock cried. “Do it. Fuck me. Yes.”

Mycroft slid his hands down Sherlock’s back, skating over his gills.

Sherlock quivered.

Mycroft grasped Sherlock’s dorsal fin, kneading the sensitive plumes, and rocked in and out, pressing his inguen against Sherlock’s with every thrust. His brother’s own cock was hard inside his body, and Mycroft could feel the length of it from through the thin, hot wall of Sherlock’s vent. The vent itself was slick and hot, clenching and unclenching rhythmically around him. Mycroft drove harder, slamming his body into Sherlock’s, taking him, claiming him.

Sherlock raked his claws down Mycroft’s back. Mycroft hissed, gave a powerful thrust of his tail, burying himself in Sherlock, and came. Jets of hot seed spurted into Sherlock’s brood pouch. Sherlock clenched and writhed and convulsed beneath him, and Mycroft was confident he had reached his pleasure, too.

He had never imagined this. He’d known intellectually, of course, that his brother was no longer a fingerling. That his tail had grown thick and strong and his limbs muscular and wiry. But he had neglected to consider that one day Sherlock would also be swept up by the Riptide, that he would long for his first taste of sexual pleasure. If he had considered it, he would have assumed that Sherlock would wait in his nest for the females of Irene’s sorority pod to come and initiate him.

But he hadn’t. He’d come to Mycroft’s nest, gills heaving, lips parted, hovering at the entrance to Mycroft’s lagoon with a desperate expression that had stirred something deep and wild within him. He hadn’t courted Mycroft -- hadn’t Sung to him -- but then Mycroft had not expected him to. Mycroft had not expected Sherlock to come to him at all. He’d never imagined Sherlock in _lek_. But he was more beautiful that Mycroft could ever have imagined. His skin had turned iridescent and his usually white fins had turned seafoam-green and his pupils had tightened into cuttlefish squiggles of arousal. Mycroft’s throat had closed when he’d seen him. He’d silently opened his arms, and Sherlock had swum into them.

Mycroft had intended to be gentle. He’d known that his brother had never been penetrated before, and while Mycroft’s cock was not as big as a female’s ovipositor, it was formidable. But Sherlock had been demanding, slamming their bodies together, his tight vent taking Mycroft’s cock greedily. And so Mycroft had grasped him with his pelvic fins and fucked him, hard and fast and brutal. And Sherlock had writhed and clenched against him. Then he’d wanted it again. And again.

Sherlock lay curled against him now, tapping his claws rhymically against Mycroft’s chest, eyelids closed. His hair floated around him like so much seaweed. Mycroft stroked it, idly twisting a curl with a claw.

“It almost isn’t fun anymore,” said Sherlock.

“The _lek_ becomes tiresome after several days,” Mycroft agreed.

“My vent is sore.”

Mycroft cleared his throat. “Next time, would you like to take me?”

Sherlock turned in Mycroft’s arms. His eyes were wide. “Yes.”

If Sherlock were female, his clutch would be fertilized by now. Mycroft’s vent had begun to ache, longing for an ovipositor to fill his brood pouch with eggs. Sherlock had no clutch to give him, of course. But his cock would still fill Mycroft’s vent nicely and quench his need.

He turned to face Sherlock, grasping his forearms. Sherlock held him, gazing into his eyes with awe. Mycroft had never seen such an expression on his brother’s face before, and he doubted he ever would again. Mycroft glanced down, and saw Sherlock’s cock emerge for the first time.

It was a bright coral-color, which surprised him. He’d not known what color he expected it to be, perhaps seafoam, like Sherlock’s _lek_ -stained fluke. But it was beautiful, strongly S shaped, and fluted at the tip. He had fewer penile barbs than Mycroft, and the ones he had were shorter. But they looked decadent. Mycroft couldn’t wait to have them inside him.

Mycroft drew Sherlock close so their bodies were touching. Sherlock didn’t need any further prompting. He grasped Mycroft’s hips tight, scratching him with his claws, and mounted him.

Mycroft cried out, thrashing his tail. Sherlock thrust his hips inexpertly, never quite hitting the right angle. Still, it was perfect. Mycroft had never wanted anything more than he wanted Sherlock inside him.

It was over quickly. Mycroft held Sherlock tight for a few moments, then let him pull free. 

“I’m sorry if that wasn’t --” Sherlock flushed.

“It was fine.”

“I know I can do better.”

“And you will. With practice.” Since when had he expected Sherlock and he would practice? He hadn’t even imagined they’d share one Riptide before this. And yet it felt right. Since Sherlock had been released into the world, Mycroft had looked after him, cared for him, made a way for him. And Sherlock had grown up beautifully, intelligent and strong. What could the two of them accomplish, if they truly worked together. How many more of their people might Sherlock, clever as he was, convince to join them, to abandon their solitary, territorial ways and form a true society?

“Can we practice now?” Sherlock nuzzled at Mycroft’s neck.

“Yes.” Mycroft laughed. “Always.”

~ ~

They did practice. Mycroft lost count of how many times they had sex, or whose turn it was to claim whom. When they weren’t fucking, they were hunting, or sleeping curled around each other. Usually by the last days of _lek_ Mycroft was beyond miserable. But this time, he wanted the Riptide to go on forever. Mycroft had never known so much pleasure. The rightness of it overwhelmed him. This was how he and Sherlock were meant to be. Together.

It was clear Sherlock felt the same. His eyes sparkled every time they met Mycroft’s. In between bouts of sex, Sherlock was affectionate, caressing Mycroft’s gills, nibbling his aural fins. When Irene and Mŏlle came to Sing to them, Sherlock had bristled, indignant that anyone would dare to interrupt them. Something had swelled in Mycroft’s chest when his brother had rejected the females, making it clear he didn’t want anyone else.

But the _lek_ was winding down. They still craved each other, but the need was less urgent. The sex was becoming slow. Lazy. This time, Mycroft rocked into Sherlock languidly, clasping him close. Their eyes locked together. The moon shone overhead, glinting off Sherlock’s skin. The iridescence was fading.

“I do not want to lose you after the Riptide.” Mycroft stroked Sherlock’s cheek with the back of his knuckles.

“What do you mean, lose me? I will still be here.”

Mycroft’s heart swelled. “I mean that I don’t want for you to return to your own nest. It has only been a week, and yet I cannot imagine sleeping without you.”

Sherlock grinned. “Because you wake me up by putting your cock against me.”

“No. No, Sherlock. I will still want to wake up beside you when the _lek_ is over. I want to spend our mornings and evenings together. I want everything which is mine to be yours.”

Sherlock chuckled. “I already take everything of yours I want.”

Mycroft smiled. “I know. But I would offer you everything. Food. Territory. Nest.” He opened his arms. “I offer you myself. Until the abyss claims me.”

Sherlock’s eyes widened. “You wish to pair bond.”

“I do.”

Sherlock glanced down, clasped Mycroft’s forearms. “Mycroft, I -- this is the _lek_ speaking.”

“No. No, Sherlock I have shared the Riptide with other lovers and never made such declarations. I assure you, my desires will remain unchanged after the _lek_ subsides.”

Sherlock shook his head. “You cannot truly want me. You think you want me because I’m appealing like this. When I want nothing more than to fuck you, to please you. But when the Riptide is over things will go back to how they were before and you will be disappointed in me and scold me and ….”

“Sherlock, I ‘scold’ you because I know you can be more than you are. I want the best of things for you. I always have. It is not because I’m truly disappointed. Quite the opposite. I am proud of you, of what you’ve become. Please believe me. My affection for you is complete and sincere. You are mine own clutchmate. I have known you since we were together in our father’s brood pouch, and I have loved you for as long.”

Sherlock pressed his lips together. His gills quivered. “And I, you, but…. Not like that, Mycroft. Not as pair-bonded lovers do.”

Sherlock’s admission was like a harpoon in his abdomen. Pain lanced through Mycroft’s belly, heat filling his chest. How could he have misjudged so badly? He had been so overwhelmed by the intensity of his own feelings he’d been certain that Sherlock must feel the same. And so he’d failed to subject his deductions about Sherlock’s behavior to proper scrutiny. If he had, he would have seen that Sherlock had been enjoying his first Riptide. Nothing more.

“I’m sorry,” Sherlock continued. “I wish that I -- I think there’s something wrong with me. You’re -- But I don’t. Feel things. Not that way.”

“I see. I miscalculated. Forgive me.” Anger rose within him. At himself, for having allowed this situation to arise.

Sherlock stroked his arm. “There’s nothing to forgive.” He nipped at one of Mycroft’s aural fins.

Mycroft flinched.

“I’m sorry,” said Sherlock. “I thought -- I still…. I don’t want things to change.”

Mycroft composed his face, smoothing his features flat. “I know that you would like to pretend this never happened. As would I. But what has been said cannot be unsaid, and change will come whether you want it or not.” He fanned his plumage around him, making himself look bigger without actually flaring into a threat display. “I think it would be best if you leave.”

Sherlock’s face crumpled. “No. Mycroft. Don’t make me go. Please.”

“Stay, then, if you wish.” He gave a great shove of his tail and made his way towards the mouth of the atoll.

Sherlock followed him.

Mycroft swept water aside with his arms, jetted forward with powerful kicks of his tail. He was the stronger swimmer. His bigger fluke propelled him through the warm water as he sped away from Sherlock, who trailed behind, unable to catch up but not letting Mycroft out of his sight.

Mycroft knew where he was going. He swam towards the edge of his territory, and he dove deep, heading towards the sea floor. Pressure built up around his chest and ears. At last he saw it. A clipper ship, lying on its side. The hull was covered in barnacles and half rotted away. Mycroft swam through a hole in the side of the vessel.

Sherlock arrived some moments later, gills flaring from exertion. He swam into the space after Mycroft. “Please,” he said, “don’t run from me.”

Mycroft coiled in the rear of the ship, next to a pile of barrels Sherlock had been rummaging through so many years ago when he’d run afoul of Taqtik.

“Please go, Sherlock. Go back to your nest. Take another lover to finish out the Riptide.”

“No. No, Mycroft, I’m not leaving you.” He ventured closer, reached for Mycroft’s hand.

Mycroft fanned his aural fins and his dorsal spines in a threat display. 

Sherlock’s eyes widened, and he pulled his hand back.

“Leave me, Sherlock. You left me here once before.” His phantom fin ached.

“I was a fingerling then.”

“And you’re acting like a fingerling now. Leave me.”

“I’m sorry. I never meant --”

“I know. I should never have put you in that position. The fault was mine. Now leave. Please.”

Sherlock bit his lip until it bled. His curls floated around his pale face. Then he turned slowly, fluke flaring out behind him, and swam towards the ragged opening at the back of the ship. He paused to look back over his shoulder.

“I do love you, you know.”

Mycroft did not respond. He coiled tightly around himself. His gills heaved. His vent ached. He wanted to reach for Sherlock, to pull him close. He would likely never have another opportunity. But it would be senseless to torture himself with the taste of what he could not have. He floated silently at the back of the ship and watched Sherlock’s white and seafoam fluke disappear into the gloom.


	3. Regard

With great reluctance, Mycroft again left Sherlock alone with his grief. He resumed his patrols around Sherlock’s island, but did not approach the grotto. He kept hoping the worst of the crisis had passed. He had pulled Sherlock from the beach into his arms, and Sherlock had clung to him, come with him. Then Mycroft had let him go. But for the first time in centuries, he almost dared to hope that Sherlock would come back to him, that their newfound intimacy would continue.

He knew this was not, however, the time to nurture future hopes. Sherlock was not out of danger. He did not leave his nest, even to hunt. This lassitude concerned Mycroft. He debated hunting for Sherlock, bringing food to the grotto. But he did not want Sherlock to think Mycroft was courting him. In any case, he suspected his brother would only refuse to eat. It was better to wait. When Sherlock was hungry enough, he would venture forth. And Mycroft would be there for him.

Three days after Mycroft had pulled Sherlock into the water, Mycroft again saw a human boat on the horizon. This one was not so grand as the _Appledore_ , nor so pathetic as the rowboat. It had two sails, both sea-urchin yellow, and the body of the boat was painted a softer shade of the same hue. The name on the side read _Honeybee_.

The intuition that had told him Sherlock was aboard the _Appledore_ informed him that John Watson was aboard the _Honeybee_. Mycroft’s stomach churned. He didn’t know what to feel. Sherlock would be overjoyed. But what if John was like Daniel? Only interested in Sherlock for the novelty? What if he left Sherlock again? Mycroft wasn’t sure his brother could survive losing John a second time.

And it would happen, even if John were loyal to Sherlock and stayed with him his whole life. Human lifespans were such paltry things. John would die, and Sherlock would grieve him anew. Wouldn’t it be better, safer, to forestall that now? It would be such an easy thing to weave wave and to roll the vessel into the ocean. To let John Watson drown, as he would have done originally had Sherlock not intervened.

But if Sherlock were to discover it, he would never forgive Mycroft. He might very well kill him, and Mycroft would not blame him, would not stop him. He had no right to take his brother’s lover away from him, whatever the pain it might spare Sherlock in the end. Sherlock had chosen John, not Mycroft. There was nothing to be done but wait.

Mycroft dove beneath the waves, heart sinking, and swam for his own nest.

 

~ ~

 

_Very Long Ago_

Mycroft dove down in the deep ocean in search of Lehosiel the Listener. He was the oldest and wisest of all the Named Ones, and lived on the seafloor and stirred but little, but Mycroft frequently sought his counsel. Mycroft swam down until the water pressed at his ears and ribs, and reached Lehosiel’s cavernous nest.

The Named One was gargantuan, with four lamp-like eyes set in a massive head atop a neck so long that Mycroft could not see his body. He paused before Lehosiel, and outstretched his arm, setting his hand against one of the whisker-like tentacles at the side of Lehosiel’s mouth. The tentacle wrapped around his wrist and began to emit a soft blue light.

 _Greetings, Mycroft,_ Lehosiel’s silent voice echoed in Mycroft’s mind.

_Greetings, Listener._

_What brings you to see me this day?_

Mycroft leaned in close to Lehosiel, so his head was nearly touching the giant snout. _I hear rumors that Irene has pair bonded with her lover Mŏlle. These two fierce females have joined their sorority pods into a single, powerful entity._

_I thought you were in favor of the unification of the undine, Mycroft._

_I am. But I want to see my own kind form a society. I fear that Irene and Mŏlle will only use their new strength to claim more territory._

_Ah._ Lehosiel was quiet for a long time.

Mycroft had long since learned to be patient with the colossal reptile. Lehosiel was almost as ancient as the ocean, and time meant nothing to him.

_Do not fear, Mycroft. Irene and Mŏlle are strong, but for now they are too caught up in their new bond and their love for one another to worry about such trivialities as territory. They pose no threat to you at this time._

_If you say so, Listener._

_I do._

Mycroft wanted to ask more questions, but the deep water weighed heavily on him, pressing against his gills.

_Thank you for your counsel, Listener._

Lehosiel nodded his massive head and released Mycroft’s wrist.

Mycroft rose to the surface slowly, so as not to strain his swim-bladder and lungs. Then he swam on a path towards his own nest. To get there, he would have to cross the territory of Taqtik. Taqtik was aggressive, and he and Mycroft were not on the best of terms. Mycroft would have to be careful not to provoke him.

He swam close to the wreck of a sunken ship near the edge of Taqtik’s territory. To his horror, the other undine was already there, and was chasing Sherlock, who appeared to be swimming for his life.

Taqtik was enormous for a male undine, far bigger than Mycroft, who hadn’t yet achieved his full adult size. He was gold in color with black and orange fins flared around him in a threat display. Sherlock swam fast in front of him, propelling his small fingerling body through the water with his black and white fluke. His sides were bloody where Taqtik had raked them with his claws.

Taqtik caught up to Sherlock, grabbing him by the fluke and swinging him around through the water.

Mycroft raced towards the two of them, claws and spines extended. He launched himself at Taqtik, clawing at his arms until he released Sherlock, who flew backwards. Taqtik whirled on Mycroft, teeth snapping, black hair whirling around his face. The two of them crashed into each other, biting and clawing, thrashing into a ball of fins and scales.

Sherlock sprang towards Taqtik, clawing down his back.

“Sherlock,” Mycroft snapped. “Get out of here!”

His brother ignored him, sinking his teeth into Taqtik’s dorsal fin.

Taqtik spun in the water, shaking Sherlock free. He made the mistake of turning his back on Mycroft.

Mycroft dug his claws into Taqtik’s shoulders and bit the vulnerable gills at the side of his neck.

Taqtik howled in pain, bucking against Mycroft. He shoved his own claws into Mycroft’s rib gills. Pain bloomed instantly across his whole side and blood clouded the water. Mycroft twisted Taqtik’s wrist and rolled away. Taqtik clawed at Mycroft’s tail, digging into his fluke, and pulled himself up the length of Mycroft’s body. His teeth clamped down on Mycroft’s adipose fin at the base. Mycroft kicked his tail. Taqtik held on, tearing away most of Mycroft’s fin.

Mycroft hissed, vision red with pain. He kicked again, tearing the fin free and pushing Taqtik backwards in the water. Taqtik shoved himself forward with a powerful thrust from his black and orange fluke and clawed at Mycroft’s rib gills again. Mycroft sunk his own claws into Taqtik’s wrists and pulled them free, then he rolled, spines extended, raking them over Taqtik’s body and releasing venom. Taqtik cried out, thrashing, clawing at Mycroft.

Sherlock attacked again, biting at Taqtik’s aural fins. Taqtik grabbed Sherlock by the hair and jerked him free, flinging him away. Mycroft dove forward, arms outstretched, and grabbed Taqtik into a tight embrace, holding him. He had only to wait for the venom to take effect.

It did. Taqtik’s struggles became more and more sluggish, and he slumped in Mycroft’s arms. Mycroft closed his teeth around his throat and tore, hot blood filling his mouth. He shoved Taqtik away from him, letting the corpse drift.

“Sherlock!”

His brother was treading water a few feet away, blood spiraling from his sides. Mycroft swam to him, running his hands over the wounds.

“Sherlock, are you all right?” Mycroft pulled him close, holding him against his chest, petting his hair.

“Yes.” Sherlock’s voice was small.

“What happened? What are you doing here? Sherlock, you know better than to be in another undine’s territory, especially someone as aggressive as Taktiq!”

“I wanted to see the shipwreck.”

Mycroft pulled back, incredulous. “Confound it, Sherlock. You could have been killed. What were you thinking?” “I thought if I were careful he wouldn’t notice me. The same as you. What are _you_ doing here, Mycroft?” “I went to see Lehosiel. I’m on my way home.”

“And you thought you could sneak across Taqtik’s territory.”

“I can fend for myself. You are still too small.”

“I would have been fine.”

“He would have killed you.”

“I was going to swim through that porthole.” Sherlock swam for the side of the ship. There was a porthole with the glass broken out. He dove through, arms first, twisting his shoulders past the rim and wriggling through the aperture like an octopus. His pelvic fins caught at the edges.

Mycroft grabbed Sherlock’s waist and held him firm, then pulled him back out. “Taqtik would have done the same. And then he would have torn your throat out. Sherlock, why are you so stupid!”

Sherlock hung his head.

“I’m not stupid.”

“You are. And if I hadn’t been here you’d be dead. Now come back with me to my nest.”

“No!”

Sherlock swam around the wrecked vessel. There was a ragged hole in one side of the cargo hold. He dove in. Mycroft followed. There were barrels inside, some of them broken open.

“Sherlock, come back this instant!”

Sherlock swam on, ignoring him. He rapped one of the barrels with his knuckles, then clawed at the lid, trying to find a way to open it.

Mycroft looked back through the aperture where they’d entered. A school of sharks had appeared. _Jetsam_.

“Sherlock.” Mycroft retreated into the ship. “Sherlock, stay back.”

His brother swam up beside him, looking out into the water.

“They must have smelled the blood,” said Mycroft. “Stay behind me.”

“I’m not afraid of sharks.”

“You should be.” He gestured to the ragged claw marks down his brother’s sides. “You’re bleeding. If you leave me, they will smell you and they will eat you.”

Sherlock sniffed. “I can outswim them.”

“No, you can’t.”

Sherlock tried to wriggle past Mycroft. Mycroft grabbed him around the waist and pulled him back. “I said, stay back!”Sherlock kicked and flailed.

The sharks moved towards the noise, interested.

Mycroft pushed Sherlock into the cargo hold of the ship.

Sherlock dove forward and attacked Mycroft’s tail, biting the bloody stub of his adipose fin, tearing what was left of it free. Mycroft cried out in pain. Sherlock swam past him, out through the aperture, and away.

“Sherlock!” Mycroft’s heart was in his throat.

His brother swam swiftly, skirting the edges of the shark pack. Mycroft followed, trailing blood. A shark snapped at his missing fin. Mycroft whirled in the water, raking his spines over the shark’s back. He clawed a second shark across the nose, and kicked a third away from him with his tail.

Sherlock swam with all his strength, disappearing in the dark water.

The sharks moved on in search of easier prey.

 

~ ~

 

_Now_

The _Honeybee_ made regular trips back and forth from Sherlock’s island. Every seven days, it would arrive and anchor on the beach, and then two days later, it would leave. For nearly a moon, Mycroft dared not approach the beach, or the grotto, sure he would be unwelcome. But his curiosity got the better of him, and one evening as the sun was setting, he swam towards the beach. He surfaced and inspected the island.

John Watson had begun construction of a small house on the beach. A rectangular stone foundation had been laid, and piles of timber were stacked next to it. John had lit a fire on the beach, and fish were roasting on a spit over it. A canvas tent was sat behind it. Sherlock lay in the shallows, his caudal fins spread out into a fan, watching John and -- Lestrade. Mycroft was surprised to see him, but Lestrade’s face and form were unmistakable. He sat at the fire next to John. The two of them were drinking, laughing -- and singing.

_Oh, Jenny Walker, Hi-oh!_

_Cheerly, man!_

_Married a hawker, Hi-oh!_

_Cheerly, man!_

_That was a corker, Hi-oh!_

Sherlock’s unmistakable baritone joined in on the chorus.

_Cheerly, man_

_O! Haulee, Hi-oh_

_Cheerly, man_

Mycroft froze. His brother’s voice. It was back. He had never thought to hear Sherlock’s voice again. And yet here his brother was singing. His heart was full to bursting with relief and gratitude.

_Oh, Polly Riddle, Hi-oh!_

_Cheerly, man!_

_Broke her new fiddle, Hi-oh!_

_Cheerly, man!_

_Right through the middle, Hi-oh!_

Mycroft swam closer to the island, though not so close as Sherlock. His brother looked well. Skin glossy and wet, gills pink and healed. Mycroft wanted to swim into the shallows, to ask the story of how Sherlock’s voice returned. But he didn’t. Instead, he dove into the water and turned away.

_Cheerly, man_

_O! Haulee, Hi-oh_

_Cheerly, man_

At the slight splash, Sherlock turned and looked over his shoulder. Mycroft was caught. Spying. Meddling. Poking his nose where he didn’t belong. Sherlock was well. He was among humans and he was happy. Mycroft was not needed. Mycroft was not wanted. He waited for his brother to chase him off. But Sherlock turned back to Lestrade and John, ignoring him. Mycroft swam away.

 

~ ~

 

The next day, Mycroft stayed in his own nest. He ceased patrolling his brother’s island. Sherlock’s own voice had returned. He could care for himself now. And he had John. Mycroft did not want to intrude on their intimacy. He was just going to sleep when he saw Sherlock’s familiar silhouette in the aperture of his atoll.

Something about his brother’s expression reminded him intensely of their first Riptide. Sherlock hung back, instead of barging in as was his wont.

“Come in,” said Mycroft, coiling his tail beneath him and rising up.

Sherlock swam into the center of the atoll. “Mycroft. I have come for you because you will not come to me. Why did you lurk in the shallows last night, instead of drawing close to the fire?”

Mycroft pressed his lips together. “It was never my intent to ‘lurk’, Sherlock. Only to protect you, as always. But I see now that you are well and you no longer need my protection, and I have let you be.”

Sherlock nodded, but he seemed unsatisfied.

“Your voice,” Mycroft began. “How?”

Sherlock smiled. “John freed me from my promise, and my voice returned to me. But you are avoiding my question, brother, just as you have been avoiding me.”

Mycroft sighed. “John has returned. I thought to leave you undisturbed.”

“You could not disturb me. For I am now so happy that even you could not vex me.”

Mycroft forced a smile. “Then I am glad.”

“Good. Be happy for me, brother mine, for John has agreed to marry me.” Sherlock reached for a thong around his neck that Mycroft noticed for the first time. A small pouch hung from it, similar to the one John used to wear. Sherlock opened it with is clawed fingers and extracted a strange lump of metal.

“What is this?” Mycroft asked.

“It is a bullet. It pierced John’s flesh. He used to wear it around his neck. Then he gave it to me. And now I am giving it to you.”

Mycroft’s brow furrowed. “Why?”

“Because John wants a ring.”

“Brother mine, you are not speaking sense.”

Sherlock smiled, eyes sparkling. “When John came back to me, I was lying on the stone bridge next to my lake.”

“Your lake?”

“You have never seen it. It is mine own secret place, deep in the heart of my nest. But John found a way there. He found a way there and he came to me. I was dying. I had found a place you could not reach me, and I had gone there to dry out and die.”

Anguish twisted Mycroft’s insides. He had left Sherlock alone to grieve, and Sherlock had tried to take his own life. He would have succeeded, if not for John. He had failed. And now he owed John Watson a debt he would never be able to repay. And to think, Mycroft had thought of killing him. If he had, he would have sealed Sherlock’s fate.

“John came, and he bid me to return to the water of my own lake, and he released me from my promise and gave me back mine on voice. Then he said that he loved me, and that we would start again, from a clean slate. But I did not want a clean slate. John still owed to me one favor. And I used it to ask him to marry me, to be my bonded, to share mine own life, the sea, mine own future Riptide, and mine own future lovers.” He touched Mycroft’s face.

Hope flared within him. He pressed it down. Surely he was mistaken. “But I thought --”

“You thought I would not return to you now that John has returned. You were wrong.”

Mycroft stared, struck dumb.

“Centuries ago, you asked me the same. To spend our mornings and evenings together. For everything that is yours to be mine.”

Mycroft’s heart pounded. “I remember.”

“I told you no. That I didn’t love you in that way. That I couldn’t love anyone in that way. But I was wrong. I am in love with John Watson. And the more I love him, the more I love everything and everyone. Including you.”

Mycroft trembled. This was not happening. He was in a dream, and he would wake, and he would be alone again.

“You were there for me when Taqtik tried to kill me. When Olizarat tried to kill John. When I tried to kill myself.”

“I will always be there for you,” said Mycroft.

Sherlock pressed the bullet into Mycroft’s palm. “When I proposed to John, I said that the bullet, which he gave me, and Olizarat’s own tooth, which I gave him, would serve for us as the symbols of our regard for one another. But John wants rings. He is planning on giving Olizarat’s own tooth to his own sister Harriet. And so I give this to you, brother mine. As a sign of mine own regard.”

Mycroft closed his hand around the small lump of metal. “Sherlock. I never expected. Never dreamed --”

“I know.”

“Are you sure? Human lovers are jealous, Sherlock. They do not take more than one partner, as we do. John will resent me, and in time, that resentment will transfer to you. I will not have you lose him so you can be with me.”

“My own Mycroft. So selfless. But you are wrong about John. He and Lestrade are lovers.”

Mycroft’s eyes widened.

Sherlock kissed Mycroft’s forehead. “And you and I are lovers.”

Mycroft floated, unsure whether to lean into the touch or pull away.

“Mine own clutchmate,” Sherlock repeated his words back to him. “I have known you since we were together in our father’s brood pouch, and I have loved you for as long. I know I do not love you as you love me, nor as I love John, but can it not be enough? Can we not be happy?”

Mycroft hesitated. Could he and Sherlock be happy? He had thought so once, and he had been proven wrong. He had resigned himself to happiness being for other creatures. Sherlock could be happy with John, for as long as John lived, and Mycroft -- Mycroft would be there for him, whatever was to come.

“Mine own brother, you do not answer me. Am I wrong? Is this no longer what you want?”

Mycroft took a deep breath. “I have wanted you for so long I cannot remember ever wanting anything else. But I had long since resigned myself to thinking you would never want me.”

“I cannot offer you a pair bond, it is true. And I cannot promise that we will never quarrel. But I do want you. I do love you.”

The flicker of hope within him returned. And this time, he did not quash it. “Then yes. Sherlock, yes. It is enough.” He had almost lost his brother forever. To share him with John was more than he had ever dared hope. Yes, he could be happy with Sherlock, and John, and Lestrade. He did not need to be the most important person in Sherlock’s world. Just to have Sherlock’s love. Even if Sherlock had said he loved him as a clutchmate only, as long as he had Sherlock’s affection and regard, it would have been enough.

Sherlock opened his arms, clearly expecting Mycroft to swim into them. Mycroft hung back. He had been alone for so long, unwanted for so long, that he was suspicious of everything that Sherlock was offering, uncertain of what had brought around this rapid change of heart. Sherlock had said his love for John was so great it made him love everything and everyone. But what if the intensity of that love were to fade? He thought again of Daniel, of the pregnant female at his side. Of Sherlock, saying he didn’t feel things. Not that way.

But the pull towards Sherlock’s arms was too strong. Mycroft could not deny his brother anything, least of all this. He would take whatever Sherlock was willing to offer, for as long as it was on offer.

Sherlock clasped him fiercely, pressing against him so they were chest to chest. Mycroft’s heart swelled. He had Sherlock’s regard. He had Sherlock’s love. He had Sherlock in his arms. A last he let himself relax, sinking into Sherlock’s chest.

“Come to my nest tonight?” Sherlock asked. “Lestrade and John will stay in their campsite on the beach.”

“Will you show me this secret lake?” Mycroft asked.

“Yes.” Sherlock laughed. “Yes.”

**Author's Note:**

> Thank you so much to everyone who has read this fic, but especially to the readers who read it as a WIP and cheered me on. I know that fanfic of fanfic is a niche genre, and I wasn't sure if anyone apart from the people the work is gifted to would read it. I appreciate all your comments so much.
> 
> Also, this work was generously commissioned by Spenglernot for Fandom Trumps Hate. Every year, the FTH mods put together a wonderful auction to benefit the charities that help the people most grievously hurt by this administration. My selected charities were Border Angels, RAICES, and RAINN. Given the crises that we have now on the border, I'm especially grateful that Spenglernot donated to these wonderful charities. If you are in a position to make a donation as well, I would encourage you to do so.


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